Structures and methods for forcing coupling of flow fields of adjacent bladed elements of turbomachines, and turbomachines incorporating the same

ABSTRACT

Turbomachines having close-coupling flow guides (CCFGs) that are designed and configured to closely-couple flow fields of adjacent bladed elements. In some embodiments, the CCFGs may be located in regions extending between the adjacent bladed elements, described herein as coupling avoidance zones, where conventional turbomachine design would suggest no structure should be added. In yet other embodiments, CCFGs are located upstream and/or downstream of rows of blades coupled to the bladed elements, including overlapping one of more of the rows of blades, to improve flow coupling and machine performance. Methods of designing turbomachines to incorporate CCFGs are also provided.

RELATED APPLICATION DATA

This application is a divisional of U.S. patent application Ser. No.14/563,204, filed Dec. 8, 2014, and entitled “Structures and Methods forForcing Coupling of Flow Fields of Adjacent Bladed Elements ofTurbomachines, and Turbomachines Incorporating the Same”, whichapplication is a continuation of U.S. patent application Ser. No.14/162,388, filed Jan. 23, 2014, and entitled “Structures and Methodsfor Forcing Coupling of Flow Fields of Adjacent Bladed Elements ofTurbomachines, and Turbomachines Incorporating the Same,” (now U.S. Pat.No. 8,926,276, issued Jan. 6, 2015); and which applications claim thebenefit of priority of U.S. Provisional Patent Application Ser. No.61/755,747, filed on Jan. 23, 2013, and entitled “Methods for ForcedCoupling of Rotor-Stator Pairs and Turbomachines Incorporating theSame.” Each of these applications is incorporated by reference herein inits entirety.

FIELD OF THE INVENTION

The present invention generally relates to the field of turbomachinery.In particular, the present invention is directed to structures andmethods for forcing coupling of flow fields of adjacent bladed elementsof turbomachines, and turbomachines incorporating the same.

BACKGROUND

Turbomachinery, including compressors, pumps, and turbines, generallyinclude a plurality of rows of bladed elements, often positioned inclose proximity to one another, that during use, form passageways for aworking fluid. Often, there is relative movement between these adjacentrows, often at very high speeds. Examples include a row of rotatingimpeller blades coupled to a rotor positioned adjacent to a row ofstationary diffuser or nozzle blades or vanes coupled to a stator.Conventional turbomachine design mandates a minimum gap between theseadjacent rows of bladed elements to minimize and avoid unwantedinteractions between the structures forming these rows, for example,rotor blades and stator vanes. These unwanted interactions include theproduction of noise and vibration, the latter of which has been known tocrack or break rotor blades and/or diffuser vanes.

SUMMARY OF THE DISCLOSURE

In one implementation, the present disclosure is directed to aturbomachine that includes an impeller rotatably disposed adjacent ashroud having a shroud surface, the impeller having a plurality ofimpeller blades, each of the impeller blades having a shroud edgeadjacent the shroud surface; and a trailing edge; and a diffuser locateddownstream of the impeller, the diffuser forming at least one diffuserpassageway; wherein the shroud surface includes a plurality of elongaterecesses located in the shroud surface and extending downstream alongthe shroud surface and into the diffuser, the recesses configured toguide a portion of a working fluid in the turbomachine.

In another implementation, the present disclosure is directed to aturbomachine that includes a first bladed element having a shroudsurface and a plurality of first blades with trailing edges; a secondbladed element; and at least one channel located in the shroud surface,a portion of the at least one channel proximate the trailing edges, theat least one channel being designed and configured to guide flow in thefirst bladed element into the second bladed element, wherein the atleast one channel is located upstream of the trailing edges and extendsdownstream into the second bladed element.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, the drawings show aspectsof one or more embodiments of the invention. However, it should beunderstood that the present invention is not limited to the precisearrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a high-level block diagram illustrating a turbomachine made inaccordance with the present invention that includes one or moreclose-coupling flow guides (CCFGs) for enhancing coupling of flow fieldsbetween adjacent bladed elements of the turbomachine;

FIG. 2 is a schematic diagram illustrating contextual features ofturbomachinery that includes a CCFG;

FIG. 3 is an exemplary bladed element in the form of a low-solidityplate diffuser having CCFGs;

FIG. 4 is an exemplary bladed element in the form of a low-solidityplate diffuser having CCFGs and a tandem row of downstream blades;

FIG. 5 is a side view of a blade having an exemplary CCFG in the form ofa contoured surface;

FIG. 6 is a perspective view of the blade shown in FIG. 5;

FIG. 7 is a front, cross-sectional view of the blade shown in FIGS. 5-6;

FIG. 8 is a front, cross-sectional view of the blade shown in FIGS. 5-7;

FIG. 9 is a front, cross-sectional view of the blade shown in FIGS. 5-8;

FIG. 10 is a front, cross-sectional view of the blade shown in FIGS.5-9;

FIG. 11 is top view of a blade having an alternative CCFG in the form ofa twisted contoured surface;

FIG. 12 is a side view of the blade shown in FIG. 11;

FIG. 13 is a perspective view of an example bladed element having ablade with the twisted contoured surface shown in FIGS. 11-12;

FIG. 14 is a perspective view of an example bladed element in the formof a diffuser having a plurality of blades and a plurality of CCFGs;

FIG. 15 is another perspective view of the bladed element shown in FIG.14;

FIG. 16 is a perspective view of the bladed element shown in FIGS. 14-15combined with another bladed element in the form of an impeller;

FIG. 17 is a perspective view of an example bladed element that does nothave a tapered hub surface;

FIG. 18 is a perspective view of an example bladed element having bladeswith CCFGs that include a chamfered surface on a pressure side of theblades;

FIG. 19 is a perspective view of an example bladed element having bladeswith CCFGs that include a chamfered surface on a suction side of theblades;

FIG. 20 is a perspective view of an example bladed element having bladeswith CCFGs that include leading and trailing edges each having astraight mid portion bounded on top and bottom by fillets;

FIG. 21 is a perspective view of an example bladed element having bladeswith CCFGs that include an alternative contoured surface;

FIG. 22 is a perspective view of an example radial compressor/pumphaving impeller blades with CCFGs that extend into a diffuserpassageway;

FIG. 23 is a close-up view of the impeller blade CCFG shown in FIG. 22;and

FIG. 24 is a perspective view of an example bladed element having bladeswith CCFGs that include ribs extending from a trailing edge of theblades along a shroud surface.

DETAILED DESCRIPTION

Referring now to the drawings, FIG. 1 illustrates a turbomachine 100made in accordance with the present invention and that includes a firstbladed element 104 and an immediately adjacent second bladed element108. Turbomachine 100 may be any type of turbomachine suitable forembodying features and aspects of the present invention, including, butnot limited to, a compressor, turbine, pump, fan, etc., regardless ofthe category of the turbomachine, i.e., regardless of whether theturbomachine is a centrifugal machine, axial machine, mixed-flowmachine, any other category of machine, or any combination thereof. Aswill become apparent to those skilled in the art from reading thisentire disclosure, each of first and second bladed elements 104 and 108can be a rotating element (e.g., a centrifugal impeller, centrifugalinducer, axial compressor wheel, axial turbine wheel, fan, pump wheel,etc.) or a stationary element (e.g., a diffuser, nozzle, flow guide,etc.).

As described below in detail, some aspects of the present invention aredirected to adding features, referred to herein and in the appendedclaims as “close-coupling flow guides” (CCFGs), to a CCFG region, hereCCFG region 112, that is generally located between adjacent bladedelements, such as bladed elements 104 and 108 of FIG. 1, and/oroverlapping with one or both of the adjacent bladed elements, in orderto intentionally closely couple the flow fields of these bladedelements. In alternative embodiments CCFG regions may also be locatedfurther upstream and/or further downstream such that they do not extendinto space 110 extending between bladed elements 104 and 108. As alsodescribed below in detail, such CCFGs may include structures that arespecifically designed and configured to enhance coupling of the flowfields of the adjacent blade regions without causing unwanted effects,such as unwanted flow, pressure, and/or vibrational disturbances. It isnoted that while FIG. 1 illustrates turbomachine 100 as having only asingle pair of adjacent bladed elements 104 and 108, in otherembodiments the turbomachine at issue may have two or more pairs ofadjacent bladed elements, and some or all of the adjacent pairs may beenhanced with CCFGs of the present invention. Before illustratingparticular CCFGs, a bit of background is first presented to provide thereader with a detailed understanding of aspects of the presentinvention.

In conventional turbomachine design, it is widely accepted that aminimum vaneless space must be maintained between adjacent blade regionsto avoid unwanted interactions between the blade regions. Examples ofsuch interactions, which can result in pressure field breakingdistortions, are included in the study by Japikse, D., 1980, “TheInfluence of Diffuser Inlet Pressure Fields on the Range and Durabilityof Centrifugal Compressor Stages,” AGARD CP-282. Indeed, the need tocontrol such vibrations has been so great that the turbomachine designworld has intensely focused on keeping this separation adequate andinvariably thinks about designing each element as a separate entity withno desire to closely couple the two. One consequence of this mindset isa common belief that good stages have little aerodynamic couplingbetween the rotor and stator, meaning little to no feedback from oneelement to the other so that neither has a significant influence on theother.

The present inventor, however, has discovered from extensive researchand testing that such conventional thinking is incorrect and that with amore sophisticated design approach, structures and features can be addedto the traditionally vaneless space, what is referred to herein as the“coupling avoidance zone,” to intentionally increase the coupling of theadjacent flow fields. This close coupling can result in increasedmachine performance, including greater work input from a compressor orpump rotor, greater work output from a turbine rotor, and greaterrelative diffusion of the flow within the impeller, among numerous otherbenefits. With the aid of modern computational methods, such ascomputational fluid dynamics, and finite element analysis, this highlycoupled three-dimensional problem can be characterized andclose-coupling features can be designed. The close-coupling featuresdescribed herein, again referred to herein and in the appended claims asCCFGs, provide multiple degrees of freedom for a turbomachinery designerto develop sophisticated structures to intentionally increase thecoupling of flow fields, resulting in improved machine performancewithout creating unwanted interactions between the blade regions and anynegative effects of those interactions, such as reduction inperformance, vibration, and noise. As will be illustrated in variousexamples below, CCFGs of the present disclosure may be located partiallyor entirely within the corresponding coupling avoidance zone and/orlocated to overlap with the upstream and/or downstream blade regions inorder to achieve the desired flow-field coupling.

In conventional turbomachine design, the minimum size of the vanelessspace, or coupling avoidance zone as noted above, can vary depending onthe type and size of the machine. For radial flow compressors and pumps,the minimum size is generally in the range of about 1.08≦r₃/r₂≦1.15,wherein r₃ is the radius from the machine centerline to the leading edgeof a vane and r₂ is the radius to the impeller or rotor trailing edge.For axial flow machines, the minimum coupling avoidance zone istypically in the range of about ¼C to ½C, wherein C is the chord lengthof the relevant blade. For mixed flow machines, the applicable metriccan be either the radial flow metric (r₃/r₂) or the axial flow metric(¼C to ½C), depending on the configuration of the machine. As describedmore fully below, CCFGs can extend into, or be fully located in, thecoupling avoidance zone, such that for radial flow compressors andpumps, r_(c)/r₂ may be less than 1.08, wherein r_(c) is the radius fromthe machine centerline to a leading edge of a CCFG, and for axial flowmachines, the separation between a leading or trailing edge of a CCFGand an adjacent blade may be less than ¼C.

FIG. 2 of the accompanying drawings introduces in further detailrelative to FIG. 1 some of the general features and principlesunderlying CCFGs described herein and exemplified with particularexamples in the remaining figures and accompanying descriptions. FIG. 2conceptually illustrates the conventional coupling avoidance zone 200described above, and its relation to the present invention. In FIG. 2,two exemplary blades 204 and 208 of corresponding respective bladedelements 212 and 216 are positioned adjacent to, but spaced from, oneanother and have corresponding respective leading/trailing edges 204Aand 208A, with the leading/trailing nature depending on the direction offlow through the machine. As noted above, each bladed element 212 and216 can be, for example, a rotor (e.g., a centrifugal impeller,centrifugal inducer, axial compressor wheel, axial turbine wheel, fan,pump wheel, etc.) or a stator (e.g., a diffuser, nozzle, flow guide,etc.), and the bladed elements may be configured for relative movement,such that one bladed element is stationary and the other rotates about arotational axis of the machine.

In accordance with the present invention, FIG. 2 illustrates a CCFGregion 220, which as discussed above contains one or more CCFGs (notshown) intentionally provided to promote flow-field coupling between theadjacent bladed elements 212 and 216. As illustrated, CCFG region 220may extend upstream and downstream of leading/trailing edges 204A and208A, may extend into or across coupling avoidance zone 200, may extendto overlap with one, the other, or both of blades 204 and 208, and mayalso extend in a circumferential direction relative to the rotationalaxis (not shown) of the turbomachine at issue (here, generally, into andout of the page). It is noted that while the extents of CCFG region 220are illustrated to extremes, the actual CCFG region used in anyparticular design need not be so. For example, in some designs, the CCFGregion will only occupy a portion of traditional coupling avoidance zone200. In other designs, the CCFG region will occupy entire couplingavoidance zone 200 and/or overlap with one, the other, or both ofadjacent bladed elements 212 and 216. In yet other designs, the CCFGregion may be located only upstream and/or downstream of couplingavoidance zone 200 and not be located in the coupling avoidance zone atall. As noted above, an important aspect of CCFGs of the presentdisclosure is the intentional flow-field-coupling effect that theycreate, and not necessarily their locations, per se.

As noted above and described in more detail below, CCFG region 220includes one or more CCFGs of one or more types. In one example, one,the other, or both of leading/trailing edges 204A and 208A,respectively, of blades 204 and 208 may be effectively moved intocoupling avoidance zone 200 by the optional addition of suitable CCFGstructures 224 and 228 (shown conceptually as dotted lines) tocorresponding respective blades 204 and 208. As illustrated, CCFGs 224and 228 may be added to one or more of blades 204 and 208, effectivelymoving leading/trailing edges 204A and/or 208A from conventional designleading/trailing edge 230 and 232 to a location in coupling avoidancezone 200. It is noted that depending on the configuration of each ofCCFG structures added, the resultant structure might look like aconventional blade in a conventional design, but the difference is thatthe blades are provided with additional functionality, i.e., theclose-coupling functionality, previously avoided by adding CCFGstructures.

As shown, each of blades 204 and 208 is located in a correspondingrespective blade region 240A and 242A of the corresponding bladedelement 212 and 216, wherein, for a rotating element, the blade regionis a volumetric space between the swept areas of the conventional designtrailing or leading edges of one or more rows of blades on a bladedelement, such as conventional design trailing/leading edges 230 and 232,when the element makes a full rotation and, for a stator element, theblade region is the same, except that rotation of the stator element isfictitious rather than actual. In conventional turbomachine design, thecoupling avoidance zone extends between the blade regions of theadjacent bladed elements, which are intentionally spaced apart tominimize the amount of flow field coupling. This is depicted in FIG. 2by coupling avoidance zone 200 extending between blade region 240A ofbladed element 212 and blade region 242A of bladed element 216.Embodiments of the present invention include the addition of a CCFG tocoupling avoidance zone 200, such that CCFG region 220 may extend beyondany meridional extent of each blade region 240A and 242A (e.g., for aradial flow device, radially outward of the radially outward-most extentof a blade region and/or radially inward of the radially inward-mostextent of a blade region).

While FIG. 2 only illustrates CCFGs 224 and 228, as described aboveCCFGs may be located anywhere within CCFG region 220. Also, while CCFGs224 and 228 are illustrated conceptually and relatively simply in FIG.2, as described and illustrated more fully herein, a CCFG of the presentdisclosure may have any one or more of a variety of differingconfigurations, including a contoured surface, rib, trough, and channel.For example, CCFGs of the present disclosure may include troughs,channels, and/or ribs in or on a hub or shroud surface, and may extendupstream or downstream of either of blades 204 and 208. CCFGs of thepresent disclosure may also include ribs, troughs, or channels locatedon the opposite side of one of blades 204 and 208 from couplingavoidance zone 200. For example, in embodiments where one of blades 204and 208 is a diffuser vane located downstream of coupling avoidance zone200, a CCFG may be located downstream of a trailing edge of the diffuservane.

As will be described more fully below in example embodiments, CCFGs inthe form of ribs and contoured surfaces may be added in combination withCCFGs in the form of troughs or channels to optimize the design. Forexample, in addition to improving flow coupling, troughs and channelsmay be used to maintain an appropriate cross-sectional area of thepseudo-passage along a cascade by cancelling out any vane blockage dueto the addition of a CCFG, such as a contoured surface.

In some embodiments, the CCFGs disclosed herein may be combined withstability and flow control holes, such as those described inInternational Patent Application No. PCT/US02/19173, titled “FLOWSTABILIZING DEVICE,” which is incorporated by reference herein for itsteachings of stability and flow control holes. Other embodiments mayinclude various noise reduction methods in addition to the design ofCCFGs, including the addition of resonators, honeycombs and surfacetreatments.

In light of the general features of turbomachinery incorporating one ormore CCFGs described above and illustrated in the accompanying figures,the following discussion and corresponding figures illustrate someexample embodiments to further explain and illustrate aspects of thedisclosure.

In some embodiments, turbomachinery incorporating CCFGs may have bladedelements having a low solidity row of airfoils or plates, such as wherethe bladed element is a diffuser, where solidity is defined as the ratioof chord length to pitch, and where a low solidity row may have asolidity ratio in the range of approximately 0.5 to 1.3. For example,low solidity may refer to minimal overlap or no overlap between any twoadjacent vanes. FIG. 3 illustrates a portion of an exemplarylow-solidity diffuser 300 having a plurality of blades 302 in the formof plates. For ease of comparison, diffuser 300 is an example of one ofbladed elements 104 or 108 (FIG. 1), and blades 302 are examples ofblades 204 or 208 (FIG. 2). In the illustrated embodiment, a leadingedge of each of blades 302 includes a CCFG, in the form of contouredsurface 304 that is designed and configured to closely couple a flowfield in an adjacent bladed element, such as an impeller, with a flowfield in diffuser 300. As will be described more fully below, contouredsurfaces 304 can provide multiple degrees of freedom for designing aCCFG for optimal coupling for a given application, and the contouredsurfaces may also act as additional structural support for blades 302,which can improve vibrational performance. Blades 302 may be configuredsuch that contoured surfaces 304 extend into a coupling avoidance zoneto more closely couple adjacent flow fields. In alternative embodiments,low-solidity diffuser 300 may also include additional CCFGs in the formof any of the CCFGs described herein. For example, CCFGs may also belocated downstream of trailing edge 306 of one or more of blades 302, ormay be located between adjacent blades. CCFGs may also be added to lowsolidity rows comprising vanes with airfoil cross-sectional shapes, andmay also be added to blade rows having higher solidity. In addition, asdescribed more fully below, blades 302 may include fillets along all ora portion of the base of the vanes to improve vane strength andvibrational performance.

FIG. 4 illustrates low-solidity diffuser 400 that includes a first lowsolidity row of blades 404 in the form of plates, and also includes asecond downstream row of tandem blades 408. In conventionalturbomachinery design, the number of downstream tandem blades istypically the same or greater than the number of upstream blades becausea primary purpose of tandem blades in conventional design is to limitthe level of loading coefficient per row. In the illustrated embodiment,however, the number of downstream tandem blades 408 may vary, from morethan the number of first row blades 404 to less than the number of thefirst row blades, including just one tandem blade 408, and the tandemblades may be full or partial height blades. In the illustratedembodiment, low-solidity diffuser 400 has 14 first row blades 404 and 6second row tandem blades 408, which is less than half the number of thefirst row blades. The illustrated embodiment does not require moretandem blades 408 than first row blades 404 because, in the illustratedembodiment, the tandem blades are designed and configured to improvestability by acting as a break for rotating stall cells, or serving as aboundary layer guide or fence to prevent flow overturning and separationor stall.

FIGS. 5-10 illustrate various aspects of an exemplary blade 500 having aCCFG in the form of contoured surface 502 formed on a leading/trailingedge 504 of the blade. In the illustrated embodiment, contoured surface502 extends from conventional leading/trailing edge 506, whichcorresponds to conventional leading trailing edge 230 or 232 (FIG. 2).Thus, the addition of contoured surface 502 to blade 500 causesleading/trailing edge 504 to extend beyond blade region 508, (whichwould correspond to blade region 240A or 242A (FIG. 2)) and into acoupling avoidance zone (not shown). Contoured surface 502 may,therefore, extend into a coupling avoidance zone of a machine andimprove flow field coupling and increase machine performance. Contouredsurface 502 may be located in certain locations of a CCFG region, whichwould correspond to CCFG region 220 (FIG. 2). Blade 500 may be locatedin any number of types of machines and may be coupled to any one of anumber of bladed elements in the machines. For example, blade 500 may bea vane of a diffuser in a compressor or pump, or may be a vane of anozzle in a turbine. In the illustrated embodiment, blade 500 extendsbetween hub 510 and shroud 512 of a bladed element (such as bladedelements 104 or 108 (FIG. 1) and is positioned in a flow passageway 520.Example contoured surface 502 is formed in leading/trailing edge 504 andhas a curved or parabolic shape with an apex 524 and includes upper leg526 and lower leg 528, each having ends 530 and 532. Contoured surface502 provides additional structure to blade 500 which may improvevibrational performance. In addition, blade 500 may also have a filletradii 600 (best seen in FIG. 6) at one or more of the base or top of theblade, and may also have an appropriate thickness distribution toincrease vibrational performance.

In the example embodiment, contoured surface 502 is substantiallysymmetrical, with apex 524 being located substantially at the midpointbetween hub surface 540 and shroud surface 542, and ends 530 and 532 ofupper and lower legs 526 and 528 being located at substantially the samedistance from apex 524. In alternative embodiments, CCFGs may include avariety of alternative contoured surface shapes, including asymmetricalshapes. For example, the location of the apex may vary, both in therelative distance between hub surface 540 and shroud surface 542, andalso the distance from ends 530 and 532. For example, example contouredsurfaces include apexes located in a coupling avoidance zone, as well ascontoured surfaces were the apex is located outside of the couplingavoidance zone and one or both of the legs of the contoured surfaceextend into the coupling avoidance zone. Alternative contoured surfacesinclude other geometric shapes, including triangular, and shapes withoutan apex. As described and illustrated in example embodiments below, thelegs may vary in length, with, for example, an upper leg being longerthan a lower leg, and having a non-planar contoured surface, such as atwisted contoured surface.

FIGS. 6-10 illustrate various cross sections of contoured surface 502when viewed from the perspective shown by arrow 602 in FIG. 6. Morespecifically, FIG. 7 illustrates a cross section of blade 500 at thebeginning of contoured surface 502 (when viewing FIG. 5, at a locationto the right of the point identified by reference numeral 524). FIGS.8-10 illustrate cross sections at locations further along blade 500 andcontoured surface 502 (when viewing FIG. 5, starting at the location tothe right of the point identified by reference numeral 524 and moving tothe left along the contoured surface). As shown, leading/trailing edge504 of contoured surface 502 narrows to a midpoint 1000 (FIG. 10) in thethickness of blade 500, forming a sharpened aerodynamic shape that mayimprove flow performance. This chevron or leading edge thinning ortapering may be located on either vane side, or both, or varydifferentially from one side to that other.

FIGS. 11-13 illustrate an alternative blade 1100 having CCFG in the formof a twisted contoured surface 1102. As with contoured surface 502,twisted contoured surface 1102 is formed in a leading or trailing edge1104 of blade 1100 that may be located in a variety of differentmachines. Unlike contoured surface 502, twisted contoured surface 1102has a twisted shape, such that upper leg 1106 curves away from blade1100 in one direction, and lower leg 1108 curves away from the blade insubstantially the opposite direction. In the illustrated embodiment,only a leading/trailing portion 1110 of blade 1100 is twisted, and theremainder of blade 1100 is substantially planar. In alternativeembodiments, a larger portion of blade 1100, including the entire lengthof blade 1100 may have a twisted configuration. FIG. 13 illustrates anexample application of twisted contoured surface 1102, located on aleading edge of blade 1300 positioned between a shroud surface 1302 andhub surface 1304 of bladed element 1306, such as one of bladed elements104 and 108 (FIG. 1).

Thus, as illustrated in FIGS. 5-13 and described in the accompanyingdescription, CCFGs in the form of contoured surfaces provide aturbomachinery designer with a large number of degrees of freedom foroptimizing geometry for a given application, including the shape of thecontoured surface, the relative lengths of the legs, and twisting of thecontoured surface, as well as the blade the contoured surface is formedin.

FIGS. 14-16 illustrate an exemplary embodiment of a bladed element inthe form of diffuser 1400 of a radial flow compressor/pump 1402utilizing various forms of CCFGs. For ease of comparison, radial flowcompressor/pump 1402 is an example turbomachine 100 (FIG. 1) anddiffuser 1400 is an example bladed element 104 or 108 (FIG. 1).Compressor/pump 1402 includes shroud 1404 and hub 1406, and a pluralityof blades 1408 extending therebetween, forming diffuser 1400. In theexample embodiment, blades 1408 form a low solidity row, and arepositioned in a blade region extending from a conventional designleading edge 1410 of the blades radially outward. Blades 1408 have CCFGsin the form of contoured surfaces 1412 that have a similar configurationas contoured surface 502 (FIG. 3). As best seen in FIG. 15, unlikecontoured surface 502, upper legs 1414 of contoured surface 1412 extendradially inward to a greater extent than lower legs 1416, and extendalong shroud surface 1418, overlapping impeller blades 1600 (FIG. 16).Thus, upper legs 1414 form ribs in shroud surface 1418, and also formtroughs 1420 extending between the ribs. Thus, unlike conventionalturbomachine design, a leading edge of blades 1408 include a CCFG in theform of contoured surface 1412 that not only extends into thetraditional coupling avoidance zone, but a portion of the contouredsurface 1412 actually overlaps a trailing edge 1602 of impeller blades1600 (FIG. 16). The illustrated configuration therefore results in ar_(c)/r₂ ratio of less than 1.0, whereas conventional design wouldforbid ratios less than about 1.08. Such a configuration allows diffuser1400 to begin to direct flow while the flow is still in impeller 1604(FIG. 16), using troughs 1420 and upper legs 1414, and continues toefficiently guide the flow into pseudo-passageways of diffuser 1400,creating close-coupling between rotor and stator flow fields.

In alternative embodiments, separate ribs or channels located betweendiffuser blades, rather than extending from a leading edge of theblades, may be utilized instead of, or in combination with the CCFGsillustrated in FIGS. 14-16. The size and shape of the ribs and channelsmay also vary. For example, while troughs 1420 in the illustratedembodiment have a width defined by upper legs 1414 extending from blades1408, narrower channels may be used, in addition to, or as analternative to troughs 1420. In addition, troughs or channels may beused downstream of blades 1408 to further enhance flow guidance andcoupling. Additional structures such as a turbulator or raised rib orriblet may also be added to one or more of the hub and shroud surfaces1422 and 1418 to generate turbulence and thereby stabilize flow byenhancing local mixing.

The various degrees of freedom of the CCFGs can be utilized by adesigner to ensure the CCFGs do not result in adverse vibrationalperformance. For example, the size of troughs 1420 may be configured tocounteract the increased space taken up by upper legs 1414 and contouredsurfaces 1412. Also, as best seen in FIGS. 14 and 16, hub and shroudsurfaces 1422 and 1418 may be tapered, with a greater height 1606 at theentrance of diffuser 1400, and a smaller height 1608 at the diffuserexit. Lowering hub surface 1422 at the diffuser entrance may, in somedesigns, improve flow coupling. Also, increasing height 1606 at thediffuser entrance can be utilized, along with troughs 1420 to balancethe additional CCFG structure added to the flow passage and minimizevane blockage. Also, as described above, the shape of contoured surface1412 can be optimized for a specific application.

FIG. 17 illustrates an alternative compressor/pump diffuser 1700 that issimilar to diffuser 1400, except that hub surface 1702 is not tapered,while shroud surface 1704 is tapered, similar to shroud surface 1418(FIGS. 14-15). In alternative embodiments, hub surface 1702 may betapered instead of shroud surface 1704. Thus, the angle of the shroudand hub surfaces 1702 and 1704 may be varied to tailor the size andcontour of the flow passageway in combination with the additional CCFGsto optimize flow.

FIGS. 18 and 19 illustrate alternative CCFG configurations.Compressor/pumps 1800 and 1900 include low solidity diffusers 1802 and1902 having a plurality of blades 1804 and 1904. Unlike compressor/pump1402, blades 1804 and 1904 have an alternative contoured surface 1806and 1906, each having a more shallow curvature than contoured surface1412. Also, unlike compressor/pump 1402, blades 1804 and 1904 havecontoured surfaces on both leading edges 1808, 1908 and trailing edges1810, 1910. Also, upper legs 1812, 1912 are shorter than upper legs 1414and do not extend up shroud surface 1814, 1914. In alternativeembodiments, contoured surfaces 1806 or 1906 may be combined with any ofthe other CCFGs disclosed herein, including troughs, channels, extendedupper legs forming ribs, as well as ribs in other locations. Blades 1804and 1904 also include fillet radii 1816 and 1916 extending along theperimeter of the top and bottom of blades. Fillet radii 1816 and 1916provide increased structural integrity to blades 1804 and 1904 andprovide a small gusset 1818, 1918 and 1820, 1920 at leading and trailingedges 1808, 1908 and 1810, 1910 of the blades.

Contoured surfaces 1806 and 1906 also include alternative leading edgedesigns, which may be utilized for differential incidence control. Morespecifically, as described above and best illustrated in FIGS. 8-10,contoured surface 502 includes a sharpened leading edge that convergesat a midpoint 1000 of blade 500. By contrast, leading edge 1808 ofcontoured surface 1806 includes a chamfered surface 1822 on a pressureside of blades 1804, and leading edge 1908 of contoured surface 1906includes a chamfered surface 1922 on a suction side of blades 1904.Thus, the leading edge of the CCFG contoured surfaces disclosed hereincan be varied, including by the selective location of a chamferedsurface to incorporate differential incidence control in the bladedesign.

FIGS. 20 and 21 illustrate additional alternative contoured surfaces2000 and 2100. As shown in FIG. 20, contoured surface 2000 is formedfrom a substantially straight mid portion 2002 bounded on top and bottomby fillets 2004 and 2006 that provides a tapered upper and lower portionto a leading edge of blade 2008. As with blades 1804 and 1904, blade2008 has a contoured surface 2000 on both leading and trailing edges.FIG. 21 illustrates a diffuser 2102 including blades 2104 in the form offlat plates, and having a contoured surface 2100. Contoured surface 2100has a rounded shape, and includes upper leg 2106 and lower leg 2108.Both upper and lower legs 2106 and 2108 have a curvature and curve awayfrom a suction side 2110 of blades 2104. Upper leg 2106 has a longerlength than lower leg 2108, and extends along shroud surface 2112,forming troughs 2114.

FIG. 22 illustrates an alternative compressor/pump 2200 having anextended impeller 2202. As best seen in FIG. 22, trailing edge 2204 ofimpeller blade 2202 that extends beyond a conventional design trailingedge 2300 (FIG. 23) (which, for convenience corresponds to conventionaldesign trailing/leading edges 230 and 232 (FIG. 1)) and extends intodiffuser passageway 2206. Extended portion 2304 (FIG. 23) of impellerblade 2202 is therefore a CCFG that is designed and configured toclosely couple the adjacent flow fields. Thus, the design ofcompressor/pump 2200 is in direct contradiction of conventional designpractices, which mandates a minimum gap between diffuser vanes andimpeller blades. Instead, portions of blade 2208 of diffuser 2210 mayextend along shroud surface 2212, overlapping impeller blade 2202 andbegin to guide flow while the flow is still in the impeller, and atrailing edge 2204 of impeller blade 2202 may overlap diffuserpassageway 2206, extending into the diffuser passageway, and efficientlyguiding and closely coupling the two flow fields. Compressor/pump 2200may also include diagonal tapering or trim of impeller trailing edge2204 to optimize the rotor-stator geometry.

FIG. 24 illustrates an alternative compressor/pump 2400 having a lowsolidity diffuser 2402 that is similar to other diffusers disclosedherein, having various CCFGs, including a contoured surface 2406 on aleading edge of blades 2408. Blades 2408 have an additional CCFG in theform of ribs 2410 extending from a trailing edge of the blades, alongshroud surface 2412. Ribs 2410 may act as an additional flow guidedownstream of blades 2408, and may also improve stability by acting as abreak for rotating stall cells, serving as boundary layer guide orfence, and preventing flow overturning and separation or stall. Ribs2410 may also be combined with troughs to form continuous troughs thatextend from the shroud surface in the impeller, through the diffuser toa vaneless space downstream of the diffuser to increase close coupling.In alternative embodiments ribs 2410 may be placed along hub surface2414 in addition to, or instead of, shroud surface 2412, and the shapeand size of the ribs may vary, including having a larger height thatextends further from shroud surface 2412, and alternative shapes,including airfoil, skewed, or curved.

Further alternative exemplary embodiments of the present invention aredescribed in the paragraphs below.

In one example, a turbomachine, including a first bladed element havinga first blade region containing a plurality of first blades; a secondbladed element having a second blade region containing at least onesecond blade, the second blade region located adjacent to the firstblade region; and a close-coupling flow guide (CCFG) designed andconfigured to, during use, closely couple a flow field of the firstbladed element with a flow field of the second bladed element. Such anexemplary turbomachine may also include one or more of the followingfeatures:

Ones of the plurality of second blades in the low solidity blade rowincludes a plurality of airfoils.

The CCFG includes a fin structure.

The contoured surface having a leading or trailing edge having amidpoint, the leading or trailing edge includes a tapering approximatelyto the midpoint.

The contoured surface having a leading edge including a chamfer.

The chamfer located on a pressure side of the contoured surface.

The chamfer located on a suction side of the contoured surface.

The second blade having a leading edge located adjacent to the firstblade region and a trailing edge located on an opposing side of thesecond blade from the leading edge, and wherein the rib extends from thetrailing edge of the second blade.

The CCFG includes a channel.

The channel overlaps the first blade region.

The channel overlaps the second blade region.

The CCFG coupled to a leading edge or trailing edge of at least oneof: 1) one of the plurality of first blades and 2) the at least onesecond blade.

The CCFG overlaps at least one of: 1) one of the plurality of firstblades and 2) the at least one second blade.

The CCFG includes a recess.

The recess overlaps the first blade region.

The recess overlaps the second blade region.

Includes a hub surface, wherein the recess is a tapered recess in thehub surface.

The first bladed element includes a rotor and the second bladed elementincludes a stator.

The second bladed element is part of a nozzle.

The second bladed element is part of a diffuser.

Includes a rotor cover, and wherein the CCFG is formed in the rotorcover.

The CCFG includes a recess.

The rotor cover has a surface facing at least one of the first blade andthe second blade, and the CCFG extends from the surface.

The turbomachine is a radial flow machine, the rotor has a rotationalaxis, the first blade has a trailing edge located at a radius, r₂, fromthe rotational axis, the CCFG has a leading edge located at a radius,r_(c), from the rotational axis, and wherein r_(c)/r₂ is greater thanzero and less than about 1.08.

The turbomachine is an axial flow machine, the first blade has a chordlength, C, and a trailing edge, the CCFG has a leading edge, and whereina distance between the leading edge and the trailing edge is less thanabout ¼ times C.

In a second alternative exemplary embodiment, a turbomachine includes afirst blade row positioned adjacent to a second blade row; and a oneclose-coupling flow guide (CCFG) located proximate to at least one ofthe first blade row and the second blade row, the CCFG being designedand configured to closely couple a flow field of the first blade rowwith a flow field of the second blade row. Such an exemplaryturbomachine may also include one or more of the following features:

The CCFG overlaps at least one of the first blade row and the secondblade row.

The feature is a tapered recess in at least one of the hub surface andthe shroud surface.

Includes a tandem blade row positioned downstream of the second bladerow, the tandem blade row having a lower blade number than the secondblade row.

In a third alternative exemplary embodiment, a method of designing aturbomachine, includes defining adjacent rows of blades; adding aclose-coupling flow guide (CCFG) to a coupling avoidance zone extendingbetween the adjacent rows of blades; and designing and configuring theCCFG to create feedback between flow fields in the adjacent rows ofblades to thereby closely couple the adjacent rows of blades.

Exemplary embodiments have been disclosed above and illustrated in theaccompanying drawings. It will be understood by those skilled in the artthat various changes, omissions and additions may be made to that whichis specifically disclosed herein without departing from the spirit andscope of the present invention.

What is claimed is:
 1. A turbomachine, comprising: an impeller rotatablydisposed adjacent a shroud having a shroud surface, said impeller havinga plurality of impeller blades, each of said impeller blades having: ashroud edge adjacent said shroud surface; and a trailing edge; and adiffuser located downstream of said impeller, said diffuser forming atleast one diffuser passageway; wherein said shroud surface includes aplurality of elongate recesses located in said shroud surface andextending downstream along said shroud surface and into said diffuser,said recesses configured to guide a portion of a working fluid in saidturbomachine.
 2. A turbomachine according to claim 1, wherein saidelongate recesses are selected from the group consisting of troughs andchannels.
 3. A turbomachine according to claim 1, wherein said elongaterecesses extend along a curved trajectory.
 4. A turbomachine accordingto claim 1, further comprising raised ribs formed on said shroud surfaceadjacent said shroud edges of said plurality of impeller blades, whereinsaid elongate recesses extend between said ribs.
 5. A turbomachineaccording to claim 4, wherein said ribs overlap said trailing edges ofsaid plurality of impeller blades and extend into said diffuserpassageway.
 6. A turbomachine according to claim 5, wherein saidrecesses overlap said trailing edges of said plurality of impellerblades and extend into said diffuser passageway.
 7. A turbomachineaccording to claim 1, wherein said diffuser further includes a pluralityof diffuser blades having leading edges, said turbomachine furthercomprising a plurality of raised ribs formed on said shroud surface,wherein at least one of said ribs extends upstream from one of saidleading edges of said diffuser blades and overlaps said trailing edgesof said plurality of impeller blades.
 8. A turbomachine according toclaim 7, wherein said diffuser blades have trailing edges, said diffuserfurther including at least one raised rib extending downstream of saidtrailing edges of said diffuser blades.
 9. A turbomachine according toclaim 8, wherein said at least one raised rib extending downstream ofsaid diffuser blades extends from one of said diffuser blade trailingedges.
 10. A turbomachine according to claim 7, wherein said diffuserblades are arranged into a low solidity blade row.
 11. A turbomachineaccording to claim 10, wherein said diffuser further includes at leastone tandem vane located downstream of said low solidity blade row.
 12. Aturbomachine according to claim 1, wherein said at least one diffuserpassageway has an entrance with a first height and an exit with a secondheight, said at least one diffuser passageway being tapered, whereinsaid first height is not equal to said second height.
 13. A turbomachineaccording to claim 12, wherein said first height is greater than saidsecond height.
 14. A turbomachine, comprising: a first bladed elementhaving a shroud surface and a plurality of first blades with trailingedges; a second bladed element; and at least one channel located in saidshroud surface, a portion of said at least one channel proximate saidtrailing edges, said at least one channel being designed and configuredto guide flow in said first bladed element into said second bladedelement, wherein said at least one channel is located upstream of saidtrailing edges and extends downstream into said second bladed element.15. A turbomachine according to claim 14, wherein said at least onechannel includes a plurality of channels in the shroud surface of thefirst bladed element.
 16. A turbomachine according to claim 15, whereinsaid second bladed element includes a plurality of second bladesdefining diffuser passageways extending between adjacent ones of saidsecond blades, wherein said plurality of channels are aligned with saiddiffuser passageways so that said channels guide flow in the firstbladed element into the diffuser passageways.
 17. A turbomachineaccording to claim 15, wherein said second bladed element includes aplurality of second blades having leading edges, at least one of saidleading edges of said second bladed element having a contoured surfacehaving at least one leg, wherein said at least one leg extends upstreamof the trailing edges and between ones of the plurality of channels.